I'm going to go out on a limb and say replace or clean your egr valve. It's right on top of the intake manifold and takes about 5-10 min to unbolt and put a new one on, wouldn't by anthing other than Oem though.I own a 96 hx and I changed all the ignition stuff and it still only got 30mpg so I bought a new egr and I was getting 42 average with half city and half highway in each tank and that's almost all spirited driving. I'm getting about 38 because I have a bad catalytic converter
'97 Hx gettin' 28MPG. Whats wrong?
- Thread starter HeX
- Start date
CORRECTION: Im actually gettin about 30 mpg. I miscalculated the last fill-up. Before that the speed sensor was broken, but Im fairly certain the miles per tank havent changed much. And Im gettin about 250 miles out of 9 gallons.
I have about 140,000 miles on it. I had the diagnostic ran on it & O2s didnt test bad.How many miles are on it? If it is a lot the O2's might be going out. The more carbon that gets on them the less effective they are.
I know with an HX the rear O2 isnt priced too bad, but the front one can cost some coin. The HX also has an EGR valve, that could maybe give a problem but that should trip a cell. The FPR could be bad also.
Your coincidental 10mpg difference tells me the EGR might be the culprit. Ill clean the EGR myself with brake cleaner first & see how that goes. Thanks.I'm going to go out on a limb and say replace or clean your egr valve. It's right on top of the intake manifold and takes about 5-10 min to unbolt and put a new one on, wouldn't by anthing other than Oem though. I own a 96 hx and I changed all the ignition stuff and it still only got 30mpg so I bought a new egr and I was getting 42 average with half city and half highway in each tank and that's almost all spirited driving. I'm getting about 38 because I have a bad catalytic converter
I removed the EGR to clean it. Wow, was it filthy!. I heavily sprayed inside the EGR & the ports. I even let it soak inside the EGR for a bit before reinstalling it. It seems to idle a bit smoother, but the CEL is on now despite resetting the ECU. I unplugged the EGR harness & it doesnt seem to makea difference. Am I to assume this means the EGR lines at the fuel rail are clogged or that maybe some particle I dislodged is now clogging the lines?Check the ports also to and from the EGR valve while you have it off. You can jump the pink and black wire to check operation your self.
haha my 91 civic lx is still at a little over 3/4 full at 160 miles driven
J32a2EK
New Member
Now reading over this i had the same problem with my buddys dads accord with his EGR vavle but his problem it was the fact the EGR was wide open so i had to delete the EGR because he throttle was going from 1k-2k back and forth. I had to wait for him to buy a new EGR but that diffently could cause some gas mile issues. EGR only for emissions.I removed the EGR to clean it. Wow, was it filthy!. I heavily sprayed inside the EGR & the ports. I even let it soak inside the EGR for a bit before reinstalling it. It seems to idle a bit smoother, but the CEL is on now despite resetting the ECU. I unplugged the EGR harness & it doesnt seem to makea difference. Am I to assume this means the EGR lines at the fuel rail are clogged or that maybe some particle I dislodged is now clogging the lines?
I havent yet had the chance to run a diagnostic on the ECU to check what code the CEL is giving since cleaning out the EGR. Since that, Ive been driving more cautiously & keeping it under 70 on the highway & hit 200 miles at the halfway mark on the gas gauge! I may have underestimated the engines sensitivity with my driving style. I'll continue to update accordingly.
The sad part is Im not, by comparison to speed-racer wannabe's. I guess the D16y5 must be treated a lil gentler. LOLSo a leadfoot is your problem? lol
A Long Overdue Response
I finally diagnosed the ECU and received the P0401 code for the EGR. I took apart the EGR chamber and it was horribly clogged! Cleaned it out along with the ports & the EGR itself and got noticeable response improvement. In the same month, I also installed a new Magnaflow header because the original one was cracked. The cars running much better, accelerating easier, and Im getting roughly 31.5mpg after all that. I also changed the Fuel Filter last week, which also helped responsiveness.
After further research, i believe my only remaining option to regain max MPG capacity is to replace the PCV valve. Unfortunately, the PCV valve is located just above the Oil Filter on HX models so its difficult to get to even with jack stands at home. Ill be visiting my buddy's shop & using his lift to get it done and I'll let you all know how that goes.
I finally diagnosed the ECU and received the P0401 code for the EGR. I took apart the EGR chamber and it was horribly clogged! Cleaned it out along with the ports & the EGR itself and got noticeable response improvement. In the same month, I also installed a new Magnaflow header because the original one was cracked. The cars running much better, accelerating easier, and Im getting roughly 31.5mpg after all that. I also changed the Fuel Filter last week, which also helped responsiveness.
After further research, i believe my only remaining option to regain max MPG capacity is to replace the PCV valve. Unfortunately, the PCV valve is located just above the Oil Filter on HX models so its difficult to get to even with jack stands at home. Ill be visiting my buddy's shop & using his lift to get it done and I'll let you all know how that goes.
have you checked your cap and rotor lately? i drive an hx and mine is getting about 33mpg right now and i was down at 28 until i changed my air filter and spark plugs. now i need to check my cap and rotor because i know i have put about 50,000 miles on them since i last changed mine, if that doesnt solve my mpg then idk what else it could be. also the pcv is super easy to change, you just pull on it and it pops right out then just push the new one in. i changed mine while doing an oil change a year ago
I forgot to mention that I installed a new cap & rotor along with new NGK plugs & wires. I also finally got to install the new PCV valve today. Once I had it on the lift doing an oil change, it was easy to get to & swap wit the added clearance to reach it & without the oil filter obstructing. The old one looks very dirty & clogged. Fortunately, I filled up my tank yesterday, so Ill see any results upon my next fill-up.have you checked your cap and rotor lately? i drive an hx and mine is getting about 33mpg right now and i was down at 28 until i changed my air filter and spark plugs. now i need to check my cap and rotor because i know i have put about 50,000 miles on them since i last changed mine, if that doesnt solve my mpg then idk what else it could be. also the pcv is super easy to change, you just pull on it and it pops right out then just push the new one in. i changed mine while doing an oil change a year ago
FYI, if you havent already, clean out your EGR chamber. That should help.
i cant wait to see you results maybe i need to change my pvc again its been awile. i bought a brand new egr valve about a year ago and thats when my mpg jumped up to about 45 on average but then it dropped back down about 6 months later to what it is now. how did you clean out the egr valve? i still have my old one maybe i will clean it and test and see if it helps